1. Technical Field
The present disclosure relates to thermoacoustic devices and method for making the same.
2. Description of Related Art
An acoustic device generally includes an electrical signal output device and a loudspeaker. The electrical signal output device inputs electrical signals into the loudspeaker. The loudspeaker receives the electrical signals and then transforms them into sounds.
There are different types of loudspeakers that can be categorized according by their working principles, such as electro-dynamic loudspeakers, electromagnetic loudspeakers, electrostatic loudspeakers and piezoelectric loudspeakers.
Thermoacoustic effect is a conversion of heat to acoustic signals. The thermoacoustic effect is distinct from the mechanism of the conventional loudspeaker, which the pressure waves are created by the mechanical movement of the diaphragm. When signals are inputted into a sound wave generator, heating is produced in the sound wave generator according to the variations of the signal and/or signal strength. Heat is propagated into surrounding medium. The heating of the medium causes thermal expansion and produces pressure waves in the surrounding medium, resulting in sound wave generation. Such an acoustic effect induced by temperature waves is commonly called “the thermoacoustic effect”.
Carbon nanotubes (CNT) are a novel carbonaceous material having extremely small size and extremely large specific surface area. Carbon nanotubes have received a great deal of interest since the early 1990s, and have interesting and potentially useful electrical and mechanical properties, and have been widely used in a plurality of fields. The carbon nanotube film used in the thermoacoustic device has a large specific surface area, and extremely small heat capacity per unit area that make the sound wave generator emit sound audible to humans. However, the carbon nanotube film used in the thermoacoustic device has a small thickness and a large area, and is likely to be damaged by the external forces applied thereon.
What is needed, therefore, is to provide a thermoacoustic device for solving the problem discussed above.